**3. Conclusion**

**2.3. Pathogenesis of crush syndrome**

98 Essentials of Hand Surgery

free radicals such as super oxide, H<sup>2</sup>

membranes.

vasculature [43, 44].

the punched hole in the 2nd metacarpal.

Compression of muscular segments of the limb is the basic mechanism underlying the pathogenesis of crush syndrome. The relative contribution of compression leading to ischaemia of the muscles and direct injury to the muscle leading to necrosis is difficult to separate. Mechanical compression alone with an adequate vascular supply (warm periphery with palpable pulses) has been shown to cause significant pathological changes in skeletal muscle by as early as 60 minutes as shown by Better and Stein and cited in Burzstein and Carlson [40]. This compares unfavourably to a warm ischaemic time of 6 hours – without compression [41], leading Burzstein and Carlson to conclude that *skeletal muscle is more sensitive to mechanical compression than ischaemia*. This may be due to the fact that in compression intramuscular pressures may reach as high as 240 mmHg [42] which is thought to compromise the microvasculature of skeletal muscle. This may cause alteration in myocyte function in terms of calcium flux across mitochondrial and plasma

In ischaemic injury however, reperfusion results in further damage to skeletal muscle result-

microvascular endothelial damage especially with reperfusion. Compounds such as super oxide dismutase (SOD) and catalase which when administered, inhibit or neutralise these radicals, have been shown to limit the reperfusion injury in the affected tissue and its micro-

**Figure 22. A, B:** Compare these AP and lateral radiographs to the clinical picture of the patient in **Figure 2**. The degree of comminution (and displacement) is worst in the proximal phalanx of the middle finger followed by the ring and small. The former two would best be fixed internally with mini plates. The small finger may get away with a lag screw fixation – the abductor digiti minimi inserts at the base while the collateral ligament attaches at the neck. The middle phalanx of the index finger also has significant comminution, but no displacement and would do well with a mini external fixator. Note

and hydroxyl ions, which cause parenchymal and


ing in the coinage of the term "reperfusion injury". The offending substances are O<sup>2</sup>

O2

A thorough understanding of the underlying mechanisms of injury will enable the primary surgeon to pay due diligence where required in detailed planning of the step by step management constantly deliberating carefully between damaged tissues to discard while treating with respect the tissues to be salvaged.
